Waterloo is a municipality in the Belgian province of Walloon Brabant. On January 1, 2006 Waterloo had a total population of 29,315. The total area is 21.03 km² which gives a population density of 1,394 inhabitants per km². One quarter of the current registered population are non-Belgian, most of whom work for institutions in Brussels, the capital of the European Union. Waterloo is also home to St. John's International School, one of the largest and oldest international schools in Belgium.